The present invention relates generally to control systems for internal combustion engines, and more particularly, to an electronic throttle servo temperature protection system.
Many previously known motor vehicle throttle controls have a direct physical linkage between an accelerator pedal and the throttle body so that the throttle plate is pulled open by the accelerator cable as the driver presses the pedal. The direct mechanical linkage includes biasing that defaults the linkage to a reduced operating position, in a manner consistent with regulations. Nevertheless, such mechanisms are often simple and unable to adapt fuel efficiency to changing traveling conditions, and add significant weight and components to the motor vehicle.
An alternative control for improving throttle control and the precise introduction of fuel air mixtures into the engine cylinders is accomplished by electronic throttle control. The electronic throttle control includes a throttle control unit that positions the throttle plate by an actuator controlled by a microprocessor based on the current operating state determined by sensors. The processors are often included as part of a powertrain electronic control that can adjust the fuel air intake and ignition in response to changing conditions of vehicle operation as well as operator control. Protection may be provided so that an electronic system does not misread or misdirect the control and so that unintended operation is avoided when portions of the electronic control suffer a failure.
Typically, the actuator or servomotor used to position the throttle plate is designed to have the maximum control effort available (motor voltage, current, duty cycle) to enhance throttle plate position response. Having a large control effort continuously available or available for maximum effort could possibly lead to overstressing the system""s physical components if a blockage of the throttle plate occurs or the mechanism encounters a mechanical limit. For example, a mechanical limit may be an open stop or a close stop. Specifically, the H-driver and the servomotor could overheat with sustained full control effort under some environmental conditions. In an effort to avoid permanent damage, some electronic systems shut down when they get to a threshold temperature.
The disadvantages associated with these conventional electronic throttle overheat protection techniques have made it apparent that a new technique for electronic throttle overheat protection is needed. The new technique should allow full control effort while preventing overheat conditions. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable electronic throttle servo temperature protection system. Another object of the invention is to allow full control effort while preventing overheat conditions.
In accordance with the above and other objects of the present invention, an electronic throttle servo overheat protection system is provided. In one embodiment of the invention, a method for controlling a positioning device associated with internal combustion engine control is provided. In accordance with the method, an electric motor actuates the positioning device. The positioning device is then commanded to change to a commanded position. The control effort required to change to the commanded position is detected. It is then determined whether the control effort exceeds a threshold for a predetermined time period. When the control effort exceeds the threshold for the predetermined time period, the control effort is reduced.
The present invention thus achieves an improved electronic throttle servo overheat protection system. The present invention is advantageous in that it will not cause mechanism failure or require significant and costly added robustness to the mechanism.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.